reader.rb in rdf-json-0.1.0

- old
+ new
@@ -2,32 +2,128 @@
   ##
   # RDF/JSON parser.
   #
   # @example Obtaining an RDF/JSON reader class
   #   RDF::Reader.for(:json)         #=> RDF::JSON::Reader
-  #   RDF::Reader.for("spec/data/test.json")
-  #   RDF::Reader.for(:file_name      => "spec/data/test.json")
+  #   RDF::Reader.for("etc/doap.json")
+  #   RDF::Reader.for(:file_name      => "etc/doap.json")
   #   RDF::Reader.for(:file_extension => "json")
   #   RDF::Reader.for(:content_type   => "application/json") 
   #
   # @example Parsing RDF statements from an RDF/JSON file
-  #   RDF::JSON::Reader.open("spec/data/test.json") do |reader|
+  #   RDF::JSON::Reader.open("etc/doap.json") do |reader|
   #     reader.each_statement do |statement|
   #       puts statement.inspect
   #     end
   #   end
   #
   # @example Parsing RDF statements from an RDF/JSON string
-  #   data = StringIO.new(File.read("spec/data/test.json"))
+  #   data = StringIO.new(File.read("etc/doap.json"))
   #   RDF::JSON::Reader.new(data) do |reader|
   #     reader.each_statement do |statement|
   #       puts statement.inspect
   #     end
   #   end
   #
   # @see http://n2.talis.com/wiki/RDF_JSON_Specification
   class Reader < RDF::Reader
     format RDF::JSON::Format
 
-    # TODO
+    ##
+    # @return [RDF::Graph]
+    attr_reader :graph
+
+    ##
+    # Initializes the RDF/JSON reader instance.
+    #
+    # @param  [IO, File, String]       input
+    # @param  [Hash{Symbol => Object}] options
+    # @yield  [reader]
+    # @yieldparam [Reader] reader
+    def initialize(input = $stdin, options = {}, &block)
+      super do
+        @graph = RDF::Graph.new
+
+        JSON.parse(@input.read).each do |subject, predicates|
+          subject = parse_subject(subject)
+          predicates.each do |predicate, objects|
+            predicate = parse_predicate(predicate)
+            objects.each do |object|
+              object = parse_object(object)
+              @graph << [subject, predicate, object]
+            end
+          end
+        end
+
+        block.call(self) if block_given?
+      end
+    end
+
+    ##
+    # Parses an RDF/JSON subject string into a URI reference or blank node.
+    #
+    # @param  [String] subject
+    # @return [RDF::Resource]
+    def parse_subject(subject)
+      case subject
+        when /^_:/ then RDF::Node.new(subject[2..-1])
+        else RDF::URI.new(subject)
+      end
+    end
+
+    ##
+    # Parses an RDF/JSON predicate string into a URI reference.
+    #
+    # @param  [String] predicate
+    # @return [RDF::URI]
+    def parse_predicate(predicate)
+      # TODO: support for CURIE predicates (issue #1 on GitHub).
+      parse_subject(predicate)
+    end
+
+    ##
+    # Parses an RDF/JSON object string into an RDF value.
+    #
+    # @param  [Hash{String => Object}] object
+    # @return [RDF::Value]
+    def parse_object(object)
+      raise RDF::ReaderError.new, "missing 'type' key in #{object.inspect}"  unless object.has_key?('type')
+      raise RDF::ReaderError.new, "missing 'value' key in #{object.inspect}" unless object.has_key?('value')
+
+      case type = object['type']
+        when 'bnode'
+          RDF::Node.new(object['value'][2..-1])
+        when 'uri'
+          RDF::URI.new(object['value'])
+        when 'literal'
+          RDF::Literal.new(object['value'], {
+            :language => object['lang'],
+            :datatype => object['datatype'],
+          })
+        else
+          raise RDF::ReaderError, "expected 'type' to be 'bnode', 'uri', or 'literal', but got #{type.inspect}"
+      end
+    end
+
+    ##
+    # Iterates the given block for each RDF statement in the input.
+    #
+    # @yield  [statement]
+    # @yieldparam [RDF::Statement] statement
+    # @return [void]
+    def each_statement(&block)
+      @graph.each_statement(&block)
+    end
+
+    ##
+    # Iterates the given block for each RDF triple in the input.
+    #
+    # @yield  [subject, predicate, object]
+    # @yieldparam [RDF::Resource] subject
+    # @yieldparam [RDF::URI]      predicate
+    # @yieldparam [RDF::Value]    object
+    # @return [void]
+    def each_triple(&block)
+      @graph.each_triple(&block)
+    end
   end # class Reader
 end # module RDF::JSON